[FFmpeg-devel] [PATCH v1 3/6] swscale: Add explicit rgb24->yv12 conversion

[Michael Niedermayer]

On Sun, Aug 20, 2023 at 07:16:14PM +0200, Michael Niedermayer wrote:
> On Sun, Aug 20, 2023 at 03:10:19PM +0000, John Cox wrote:
> > Add a rgb24->yuv420p conversion. Uses the same code as the existing
> > bgr24->yuv converter but permutes the conversion array to swap R & B
> > coefficients.
> > 
> > Signed-off-by: John Cox <jc at kynesim.co.uk>
> > ---
> >  libswscale/rgb2rgb.c          |  5 +++++
> >  libswscale/rgb2rgb.h          |  7 +++++++
> >  libswscale/rgb2rgb_template.c | 38 ++++++++++++++++++++++++++++++-----
> >  libswscale/swscale_unscaled.c | 24 +++++++++++++++++++++-
> >  4 files changed, 68 insertions(+), 6 deletions(-)
> > 
> > diff --git a/libswscale/rgb2rgb.c b/libswscale/rgb2rgb.c
> > index 8707917800..de90e5193f 100644
> > --- a/libswscale/rgb2rgb.c
> > +++ b/libswscale/rgb2rgb.c
> > @@ -83,6 +83,11 @@ void (*ff_bgr24toyv12)(const uint8_t *src, uint8_t *ydst,
> >                         int width, int height,
> >                         int lumStride, int chromStride, int srcStride,
> >                         int32_t *rgb2yuv);
> > +void (*ff_rgb24toyv12)(const uint8_t *src, uint8_t *ydst,
> > +                       uint8_t *udst, uint8_t *vdst,
> > +                       int width, int height,
> > +                       int lumStride, int chromStride, int srcStride,
> > +                       int32_t *rgb2yuv);
> >  void (*planar2x)(const uint8_t *src, uint8_t *dst, int width, int height,
> >                   int srcStride, int dstStride);
> >  void (*interleaveBytes)(const uint8_t *src1, const uint8_t *src2, uint8_t *dst,
> > diff --git a/libswscale/rgb2rgb.h b/libswscale/rgb2rgb.h
> > index 305b830920..f7a76a92ba 100644
> > --- a/libswscale/rgb2rgb.h
> > +++ b/libswscale/rgb2rgb.h
> > @@ -79,6 +79,9 @@ void    rgb12to15(const uint8_t *src, uint8_t *dst, int src_size);
> >  void ff_bgr24toyv12_c(const uint8_t *src, uint8_t *ydst, uint8_t *udst,
> >                        uint8_t *vdst, int width, int height, int lumStride,
> >                        int chromStride, int srcStride, int32_t *rgb2yuv);
> > +void ff_rgb24toyv12_c(const uint8_t *src, uint8_t *ydst, uint8_t *udst,
> > +                      uint8_t *vdst, int width, int height, int lumStride,
> > +                      int chromStride, int srcStride, int32_t *rgb2yuv);
> >  
> >  /**
> >   * Height should be a multiple of 2 and width should be a multiple of 16.
> > @@ -128,6 +131,10 @@ extern void (*ff_bgr24toyv12)(const uint8_t *src, uint8_t *ydst, uint8_t *udst,
> >                                int width, int height,
> >                                int lumStride, int chromStride, int srcStride,
> >                                int32_t *rgb2yuv);
> > +extern void (*ff_rgb24toyv12)(const uint8_t *src, uint8_t *ydst, uint8_t *udst, uint8_t *vdst,
> > +                              int width, int height,
> > +                              int lumStride, int chromStride, int srcStride,
> > +                              int32_t *rgb2yuv);
> >  extern void (*planar2x)(const uint8_t *src, uint8_t *dst, int width, int height,
> >                          int srcStride, int dstStride);
> >  
> > diff --git a/libswscale/rgb2rgb_template.c b/libswscale/rgb2rgb_template.c
> > index 8ef4a2cf5d..e57bfa6545 100644
> > --- a/libswscale/rgb2rgb_template.c
> > +++ b/libswscale/rgb2rgb_template.c
> 
> 
> > @@ -646,13 +646,14 @@ static inline void uyvytoyv12_c(const uint8_t *src, uint8_t *ydst,
> >   * others are ignored in the C version.
> >   * FIXME: Write HQ version.
> >   */
> > -void ff_bgr24toyv12_c(const uint8_t *src, uint8_t *ydst, uint8_t *udst,
> > +static void rgb24toyv12_x(const uint8_t *src, uint8_t *ydst, uint8_t *udst,
> 
> this probably should be inline
> 
> also i see now "FIXME: Write HQ version." above here. Do you really want to
> add a low quality rgb24toyv12 ?
> (it is vissible on the diagonal border (cyan / red )) in
>  ./ffmpeg -f lavfi -i testsrc=size=5632x3168 -pix_fmt yuv420p -vframes 1 -qscale 1 -strict -1 new.jpg
> 
>  also on smaller sizes but for some reason its clearer on the big one zoomed in 400% with gimp
> (the gimp test was done with the whole patchset not after this patch)

Also the reason why its LQ and looks like it does is because
1. half the RGB samples are ignored in computing the chroma samples
2. the chroma sample locations are ignored, the locations for yuv420 are reaonable standard

this needs some simple filter to get from a few RGB samples to the RGB sample co-located
with ths UV sample before RGB->UV

thx

[...]

-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Everything should be made as simple as possible, but not simpler.
-- Albert Einstein
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